Representational state transfer (“REST”) is a software architecture for distributed systems, such as the World Wide Web. In a REST architecture, servers hold resources such as web page content, documents, images and other types of information that are addressable by a client. A client wishing to create or modify a resource sends data representing the resource to the server, which stores the data in a repository such as a database. A Content Management System (CMS) is a computer program that allows users to, among other things, edit and maintain the resources via a graphical user interface (GUI). Some CMS applications execute on the server and interact with a browser executed by the client. Such CMS applications can provide GUI-based authoring and editing tools that are operable using the existing functionality of the browser, for example, in the form of a Hypertext Markup Language (HTML) document or other structured document that is rendered by the browser. Some such authoring tools can be rendered in a separate frame of a browser window displaying the resource, or in an entirely separate browser window.